The preferred treatment for a variety of heart conditions involves the application of electrical stimulating pulses to the heart. Appropriate courses of treatment sometimes require that such pulses be delivered to the left side of the heart and, in particular, the left ventricle. Historically, epicardial type electrodes were secured to the exterior of the heart near the apex for the purpose of delivery of such pulses. The procedure used to apply such electrodes is highly invasive and traumatic to the patient. To avoid such trauma, in recent years considerable development has occurred related to leads that can be inserted via the coronary sinus through the great vein of the heart and into the branch veins which descend from the great vein toward the apex of the heart. Current lead fixation systems on coronary vein leads are maneuverable within the vasculature but require the lead to be wedged into a narrowing vessel to achieve fixation.
Several problems exist with current fixation mechanisms, particularly when the lead and cardiac rhythm management device are being used to treat congestive heart failure. First, given the dilated nature of the heart suffering from congestive heart failure and the generally unhealthy condition of the vessels and myocardium, it is not certain that current fixation mechanisms will perform adequately. Second, current fixation designs require the electrode of the lead to be placed at or near the apex where the vessels are smaller in diameter. This location may be best with regard to fixation, but may not be the best location in terms of therapy. Emerging clinical data indicates that a mid-ventricular pacing site may be preferred in some patients suffering from congestive heart failure.
In view of the foregoing there is a real need for a fixation apparatus that will achieve lead fixation at the best location in terms of therapy even if this location is in a larger part of the vessel. More specifically, there is a need for a suitable fixation device that permits fixation of the lead at the apex, base, or mid-ventricular sites.